ABSTRACT This F32 project aims to advance translation of pre-exposure prophylaxis (PrEP) for HIV prevention for pregnant women at high risk of HIV infection. Nearly 80% of young women living with HIV worldwide reside in sub-Saharan Africa and new infections among young women are double that of young men in the region. HIV incidence is an estimated ~2-8% in women residing in high HIV prevalence regions during pregnancy and postpartum?an incidence rate similar to high-risk groups like female sex workers and HIV-serodiscordant couples. Acute HIV infection among pregnant and breastfeeding women poses a double burden in sub- Saharan Africa where acute maternal HIV accounts for 26% of all mother-to-child transmissions of HIV. PrEP is a female-controlled HIV prevention strategy that reduces HIV incidence in adherent women and could prevent HIV in pregnant women who are unable to negotiate HIV prevention within partnerships. The World Health Organization recommends PrEP for all individuals at substantial risk (>3% incidence rate) of HIV acquisition and PrEP is currently being rolled out programmatically in Kenya, including in pregnant women. PrEP adherence among pregnant African women has not been systematically evaluated to date. The proposed F32 research proposal leverages data from an ongoing cluster-randomized trial of PrEP implementation for HIV prevention in pregnant women (R01 AI125498-01, PI: John-Stewart) to evaluate open-label PrEP uptake and adherence. In Aim 1, we will use baseline data to determine predictors of open-label PrEP uptake among women who are offered PrEP during antenatal care. Identification of PrEP uptake predictors will inform who may need intensified counseling to optimize PrEP provision. In Aim 2, we will evaluate whether PrEP adherence declines during the postpartum period among women who initiate PrEP in pregnancy using longitudinal modeling of drug level data. Results from Aim 2 will contribute to understanding PrEP adherence in real-world settings using drug detection in blood samples. This will be the first study to evaluate PrEP adherence among pregnant women and will provide data to inform PrEP adherence interventions for this important population. The proposed research plan will prepare the F32 candidate for independent research as a nurse-scientist and provide rigorous postdoctoral training including 1) experience analyzing data from interventional studies, 2) formal training in new methods?including use of biomarker data in clinical research and longitudinal analyses with repeated measures and 3) development of content area expertise in PrEP adherence, an emerging area critical to effectiveness of this powerful HIV prevention strategy.